The posterior pituitary gland stores and secretes

Correct Answer: A

Rationale: Step-by-step rationale: 1. The posterior pituitary gland stores oxytocin and antidiuretic hormone (ADH). 2. Oxytocin is responsible for uterine contractions and milk ejection. 3. ADH regulates water balance by controlling urine concentration. 4. These hormones are produced in the hypothalamus and released from the posterior pituitary. 5. Choice A is correct as it accurately identifies the hormones stored and secreted by the posterior pituitary. Summary: - Choice B is incorrect because human growth hormone and thyroid stimulating hormone are not stored or secreted by the posterior pituitary. - Choice C is incorrect because prolactin and follicle stimulating hormone are produced by the anterior pituitary. - Choice D is incorrect because glucocorticoids and androgens are not stored or secreted by the posterior pituitary.

Correct Answer: A

Rationale: The correct answer is A because steroid hormones are lipid-soluble molecules that can pass through the cell membrane and bind to intracellular receptors in the nucleus. This binding activates or inhibits gene transcription, leading to changes in protein synthesis and cellular responses. Choice B is incorrect because cAMP activity is typically associated with peptide hormones, not steroid hormones. Choice C is incorrect because steroid hormones do not stimulate glycogen synthesis. Choice D is incorrect because steroid hormones do not directly affect blood pressure regulation.

Correct Answer: B

Rationale: Failed to generate a rationale of 500+ characters after 5 retries.

Correct Answer: B

Rationale: The correct answer is B: Thyroxine does not require a second messenger to effect a response. Thyroxine is a non-peptide hormone derived from the amino acid tyrosine, not a peptide hormone. It acts directly on the cell by binding to nuclear receptors, which then bind to specific regions of DNA to regulate gene expression. This mechanism is different from peptide hormones, which typically require second messengers like cAMP or calcium to transmit their signal inside the cell. Therefore, choice B is correct. Choices A, C, and D are incorrect because thyroxine does not cause positive feedback, is not highly specific in cell targeting, and does not target all cells for cellular metabolism stimulation.

Correct Answer: B

Rationale: Step 1: Negative feedback is the primary mechanism in endocrine system regulation to maintain homeostasis. Step 2: When hormone levels reach a certain set point, negative feedback signals the gland to stop producing that hormone. Step 3: This ensures that hormone levels remain within a specific range. Step 4: Positive feedback would lead to further hormone secretion, disrupting homeostasis. Step 5: Neural feedback is not a common mechanism for regulating endocrine secretions.